Introduction

Uses for Hyperosmotic Laxatives

Constipation

Glycerin (rectally),238239240241242 sorbitol (rectally),a and polyethylene glycol (PEG) 3350 (MiraLAX; orally)244 may be used for relief of occasional constipation.238239240241242244 However, rectal suppositories or enemas should not be used when oral laxatives are effective.b

Glycerin and sorbitol may be used to treat constipation occurring during pregnancy or the puerperium; however, bulk-forming laxatives or stool softeners are usually preferred.b

Avoid use of laxatives in infants and children; treat childhood constipation by counseling parents regarding acceptable variations in the frequency of bowel movements.b

Bowel Cleansing

PEG 3350 electrolyte solutions are used to empty the bowel prior to colonoscopy and barium enema radiologic examinations.245246247248252253 Glycerin and sorbitol also have been used prior to these procedures, but these laxatives do not always entirely empty the colon.b

The American Society of Colon and Rectal Surgeons (ASCRS), American Society for Gastrointestinal Endoscopy (ASGE), and Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) recommend the use of PEG 3350 electrolyte solutions in patients with electrolyte or fluid imbalances (e.g., those with renal or liver insufficiency, CHF, liver failure, advanced liver disease with ascites).251259 These experts also recommend use of PEG 3350 electrolyte solutions for colonic cleansing in infants and children.251

Sorbitol as an Adjunct to Sodium Polystyrene Sulfonate

Sorbitol is used orally or rectally to facilitate the passage of sodium polystyrene sulfonate (a resin) through the intestinal tract, prevent constipation caused by the resin, aid in potassium removal, and improve the palatability of the resin.b256

Hyperosmotic Laxatives Dosage and Administration

General

Prior to bowel cleansing, provide a copy of the patient information provided by the manufacturer containing careful instructions on the proper methods of reconstitution and administration of the laxatives.245246247248253

Administration

Administer sorbitol rectally; may administer orally when used as an adjunct to sodium polystyrene sulfonate.a

Reconstitution

When used for constipation, reconstitute PEG 3350 powder for oral solution (MiraLAX) with 120–240 mL of water (cold, room temperature, or hot).244

When used for bowel cleansing, reconstitute PEG 3350 powder (with electrolytes) for oral or nasogastric solution with the appropriate amount of lukewarm water as directed by the manufacturer.245246247248252253

Shake solution vigorously until ingredients are dissolved; additional ingredients (flavorings other than those provided by the manufacturers) not recommended.245246247248253

Refrigerate the reconstituted solution.245246247248252253 Palatability of oral solution may be increased if the reconstituted solution is chilled prior to administration;245247 however, a chilled PEG 3350 electrolyte solution is not recommended for infants.253

Administration of PEG 3350 Electrolyte Solution for Bowel Cleansing

Fast for approximately 3 or 4 hours before administration of PEG 3350 electrolyte solution.245246247253 Do not eat solid foods for at least 2 hours prior to administration.245246247252253

Administer PEG 3350 electrolyte solutions orally, but may give through a nasogastric tube if patients are unwilling or unable to drink the solution.245246247

PEG 3350 electrolyte solutions may be given by single-dose regimens (usually on the evening prior to the colonoscopy [e.g., 6 p.m.] or if procedure is scheduled for midmorning or later allowing patients 3 hours for drinking and 1 hour for complete bowel evacuation)245248251261262 or by divided-dose regimen (usually consuming a portion on the evening prior to the colonoscopy and the remaining solution on the morning of the colonoscopy).248251261262

Clinical studies suggest that the divided-dose PEG 3350 electrolyte solution regimen (e.g., 2–3 L the evening before and 1 L the morning of the procedure) is superior to the standard single-dose regimen (e.g., 4 L administered on the evening prior to the procedure).251261262

In one study, PEG 3350 electrolyte solution consumption <5 hours before colonoscopy was superior to a regimen administered ≥19 hours before the procedure.251260 If a patient has an afternoon colonoscopy, administer a portion of the PEG 3350 solution on the morning of the colonoscopy to improve bowel cleansing results.251260

Administration Precautions (PEG 3350 Electrolyte Solution)

Use PEG 3350 electrolyte solutions with caution in patients with impaired gag reflex, unconscious or semiconscious patients, and those prone to regurgitation or aspiration; observe these patients during administration, especially if solution is administered through a nasogastric tube.245246247248252

Rectal Administration (Glycerin)

Moisten regular glycerin suppositories with lukewarm water prior to insertion.b With steady pressure, gently insert suppository tip high into rectum.b238240241254255 Instruct patient to retain the suppository for 15 minutes; not required to melt to produce laxative action.238240241254255 Discontinue use if resistance is encountered.239

Before administering glycerin laxative enemas, have patient initially lie on left side with right knee bent and arms resting comfortably239242 or kneel on the bed with the head and chest lowered and forward until the left side of the face is resting on the surface of the bed.b With steady pressure, insert enema nozzle into rectum with side-to-side movement with tip pointing toward navel until the entire dose is expelled.b239242 While squeezing the container, remove tip from rectum and discard unit.239242 Discontinue use if resistance is encountered.239242 Enema fluids, if properly introduced, usually provide adequate evacuation if retained until definite lower abdominal cramping is felt.b

Dosage

Administer laxatives at infrequent intervals in single dosesa at the lowest effective dosage level, and usually for periods not exceeding 1 week; use for longer periods only under the management of a clinician and as part of a carefully planned therapeutic regimen.b

Warnings/Precautions

Warnings

Long-term or Chronic Use

Long-term use of laxatives has been associated with laxative dependence, chronic constipation, and loss of normal bowel function.b

Chronic use or overdosage of laxatives may produce persistent diarrhea, hypokalemia, loss of essential nutritional factors, and dehydration.b

Seizures Associated with Electrolyte Abnormalities

Generalized tonic-clonic seizures associated with electrolyte abnormalities (e.g., hyponatremia, hypokalemia) have been reported following use of PEG 3350 electrolyte solutions for bowel cleansing in patients without a history of seizures.248 Such neurologic effects resolved with correction of fluid and electrolyte abnormalities.248

Ulcerative Colitis

Combined Preparations

When used in combination with bisacodyl, consider the precautions, cautions, and contraindications associated with bisacodyl.252

If large volumes of liquid containing sugars (e.g., Gatorade) are added to PEG 3350 (with electrolytes) powder for solution, the sugars may reach the colon and be converted to methane or other flammable gases.259 If electrocautery is used for polyp removal, possible risk that such gases could ignite and explode.259

Sensitivity Reactions

General Precautions

Phenylketonuria

Individuals with phenylketonuria and other individuals who must restrict their intake of phenylalanine should be warned that MoviPrep (PEG 3350 electrolyte solution) contains aspartame (NutraSweet), which is metabolized in the GI tract to provide a maximum of 2.33 mg of phenylalanine per treatment (2 L of solution).248264265266267268

Glucose-6-Phosphate Dehydrogenase (G-6-PD)

MoviPrep (PEG 3350 electrolyte solution) contains 5.9 g of sodium ascorbate and 4.7 g of ascorbic acid.248 Use with caution in patients with G-6-PD deficiency (especially those with active infection, history of hemolysis, or taking concomitant drugs known to precipitate hemolytic reactions),248 since patients with G-6-PD deficiency have developed hemolysis after large IV or oral doses of ascorbic acid.263

GI Effects

Glycerin: If rectal bleeding occurs, discontinue the drug and consult a clinician.238239241

PEG 3350 solution (MiraLAX): If rectal bleeding, nausea, bloating, cramping, or abdominal pain worsens, or the patient requires >7 days of use or experiences diarrhea, discontinue the drug and contact a clinician.244

Specific Populations

Pregnancy

Lactation

Not known whether PEG 3350 electrolyte solution is distributed into milk.248 Use with caution in nursing women.248

Pediatric Use

Avoid use of laxatives in infants and children; childhood constipation is best treated by counseling parents on acceptable variations in the frequency of bowel movements.b

Safety and efficacy of glycerin preparations not established in pediatric patients <2 years of age.238239240241242

PEG 3350 (MiraLAX): Safety and efficacy not established in pediatric patients <17 years of age.244

PEG 3350 electrolyte solutions (NuLYTELY, Trilyte): Safety and efficacy not established in pediatric patients <6 months of age.246253 Closely monitor children <2 years of age receiving NuLYTELY for signs of hypoglycemia.246

Renal Impairment

Use laxative products containing >50 mEq of magnesium, >25 mEq of potassium, or ≥1 mEq of sodium per dose with caution in patients with renal disease and only under supervision of a clinician.b Monitor electrolytes.b

Sorbitol 70% Solution

Rectal

Glycerin Suppositories

Actions

When administered rectally, glycerin and sorbitol exert hygroscopic and/or local irritant action, drawing water from the tissues into feces and reflexively stimulating evacuation.b240

PEG 3350 electrolyte solution is a nonabsorbable solution that passes through the bowel without net absorption or secretion; therefore, substantial fluid and electrolyte shifts are avoided.245246247248251253259

Importance of advising patients to drink 240 mL (8 ounces) of PEG 3350 electrolyte solution every 10 minutes; rapid drinking of each portion is preferable to drinking small amounts continuously.245246247253

Abdominal bloating and distention may develop before bowel movement; if severe discomfort or distention occurs, stop drinking the solution temporarily or drink each portion at longer intervals, until symptoms abate.245246248253

Inform patients taking PEG 3350 solution (MiraLAX) that it may take 1–3 days after starting the drug to have a bowel movement.244

Importance of informing patients taking PEG 3350 electrolyte solutions and bisacodyl (HalfLytely) to avoid consumption of large quantities of water during or after preparation for colonoscopy.252

Instruct patients to take other oral drugs at least 1 hour before administering PEG 3350 electrolyte solution to minimize possible interference with absorption.245246247248252

Importance of informing clinicians before using laxatives if abdominal pain, nausea, or vomiting is present, if there has been any sudden change in bowel habits lasting >2 weeks reported, or if use of laxatives for 1 week has had no effect.b238239241242244

Importance of discontinuing use and informing a clinician if rectal bleeding develops or a bowel movement fails to occur after use; possible symptoms of a serious condition.238239241242244

Importance of not using laxative products for >1 week unless directed by a clinician.b238244

Importance of informing clinicians of existing or contemplated concomitant therapy (especially other laxatives), including prescription and OTC drugs, as well as any concomitant illnesses.244

Importance of taking only as prescribed; do not increase dosage or duration of therapy unless otherwise instructed by a clinician.244

Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.244243245246247248251253

Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

251. Wexner SD, Beck DE, Baron TH et al. American Society of Colon and Rectal Surgeons, American Society for Gastrointestinal Endoscopy, Society of American Gastrointestinal and Endoscopic Surgeons. A consensus document on bowel preparation before colonoscopy: prepared by a task force from American Society of Colon and Rectal Surgeons, American Society for Gastrointestinal Endoscopy, and Society of American Gastrointestinal and Endoscopic Surgeons. Gastrointest Endosc. 2006; 63:894-909. Available from website. Accessed 2007 Aug 8. [PubMed 16733101]

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